Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/include/linux/mailbox/mtk-cmdq-mailbox.h b/include/linux/mailbox/mtk-cmdq-mailbox.h
index ccb7342..e6f54ef 100644
--- a/include/linux/mailbox/mtk-cmdq-mailbox.h
+++ b/include/linux/mailbox/mtk-cmdq-mailbox.h
@@ -20,6 +20,9 @@
 #define CMDQ_WFE_WAIT			BIT(15)
 #define CMDQ_WFE_WAIT_VALUE		0x1
 
+/** cmdq event maximum */
+#define CMDQ_MAX_EVENT			0x3ff
+
 /*
  * CMDQ_CODE_MASK:
  *   set write mask